[Qemu-devel] [PATCH] Make -kernel flag optional on ARM.

[Grant Likely <grant.likely@linaro.org>]

Sometimes we want to boot the system via firmware instead of loading a
kernel into ram with the -kernel parameter. This patch makes the -kernel
parameter optional so that a bios image provided by the -pflash flag
will be executed.

For example:
qemu-system-arm -M vexpress-a15 -pflash <filename>

Note: Currently the file must be at least the size of the emulated flash
device (64M) otherwise QEMU will silently not use the data. This will be
fixed in a separate patch

This is part of the larger solution. For this to work it requires the
platform to have flash mapped or aliased to address 0 so that there is
some code for the emulator to execute.

Signed-off-by: Grant Likely <grant.likely@linaro.org>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel@nongnu.org
---

 hw/arm/boot.c | 47 ++++++++++++++++++++++-------------------------
 1 file changed, 22 insertions(+), 25 deletions(-)

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 7c0090f..3b9e108 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -361,12 +361,6 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
     int big_endian;
     QemuOpts *machine_opts;
 
-    /* Load the kernel.  */
-    if (!info->kernel_filename) {
-        fprintf(stderr, "Kernel image must be specified\n");
-        exit(1);
-    }
-
     machine_opts = qemu_opts_find(qemu_find_opts("machine"), 0);
     if (machine_opts) {
         info->dtb_filename = qemu_opt_get(machine_opts, "dtb");
@@ -403,26 +397,29 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
     info->initrd_start = info->loader_start +
         MIN(info->ram_size / 2, 128 * 1024 * 1024);
 
-    /* Assume that raw images are linux kernels, and ELF images are not.  */
-    kernel_size = load_elf(info->kernel_filename, NULL, NULL, &elf_entry,
-                           NULL, NULL, big_endian, ELF_MACHINE, 1);
-    entry = elf_entry;
-    if (kernel_size < 0) {
-        kernel_size = load_uimage(info->kernel_filename, &entry, NULL,
-                                  &is_linux);
-    }
-    if (kernel_size < 0) {
-        entry = info->loader_start + KERNEL_LOAD_ADDR;
-        kernel_size = load_image_targphys(info->kernel_filename, entry,
-                                          info->ram_size - KERNEL_LOAD_ADDR);
-        is_linux = 1;
-    }
-    if (kernel_size < 0) {
-        fprintf(stderr, "qemu: could not load kernel '%s'\n",
-                info->kernel_filename);
-        exit(1);
+    if (info->kernel_filename) {
+        /* Assume that raw images are linux kernels, and ELF images are not.  */
+        kernel_size = load_elf(info->kernel_filename, NULL, NULL, &elf_entry,
+                               NULL, NULL, big_endian, ELF_MACHINE, 1);
+        entry = elf_entry;
+        if (kernel_size < 0) {
+            kernel_size = load_uimage(info->kernel_filename, &entry, NULL,
+                                      &is_linux);
+        }
+        if (kernel_size < 0) {
+            entry = info->loader_start + KERNEL_LOAD_ADDR;
+            kernel_size = load_image_targphys(info->kernel_filename, entry,
+                                              info->ram_size - KERNEL_LOAD_ADDR);
+            is_linux = 1;
+        }
+        if (kernel_size < 0) {
+            fprintf(stderr, "qemu: could not load kernel '%s'\n",
+                    info->kernel_filename);
+            exit(1);
+        }
+        info->entry = entry;
     }
-    info->entry = entry;
+
     if (is_linux) {
         if (info->initrd_filename) {
             initrd_size = load_image_targphys(info->initrd_filename,
-- 
1.8.1.2